Steam Line valve selection

[gatossi]

Hello,
I have a drip leg on a 300# - SS316L line where I have to select a couple of "block" valves (1" size)
Previously the line was 2" and we had gate valves installed (Press 30barg, Temperature 300ºC, that's why we didn't use ball or plug valves)

The vendors catalogues for SS gate valves go down to 1.1/2".

Which valve would you recomend me to use there?

Gabriel

 

[unclesyd]

All our small valves on 300# steam are CS Globe Valves.

Our 650# spec for small valves are also Globe.

 

[gerhardl]

Hello,

If drip leg = draining point (with or without steamtrap) and the purpose is draining and/or blowing out dirt/condensate, a good quality ball valve with graphite sealings suitable for given pressure and temperature could be used for this 'end of line use'.

Ask for steam references. CS recommended, SS if solid and steam references from supplier.

Needle valves in SS (Note correct sealings for steam temperature and pressure required) can be used as rough regulating valves, but not suitable for 'dirt /cleaning' as dirt could clog the reduced, angeled conduit.

For inline use: ball valves could be used for steam, but note: cavitation will occur almost immidiately if not 100% closed and thight. Remember steam velocity is usually 15m/s (90 feet/s or up to about double)

Good quality suitable globe valves recommended (as above) as a general solution for inline valves.

 

[gatossi]

Firstly I want to thank both of you...

All other steam trap legs are installed on CS lines, but this one is intalled on a SS line (I'm not pretty sure why)

Is it recomendable to install a CS valve on a SS Line, won't that acelerate corrosion (I know steam is not likely to be corrosive, but there will be a galvanic couple there)

Regards,

Gabriel

 

[gerhardl]

Hello again,

CS is recommended mostly for economical and commercial availability reasons. Of course SS is best on a material basis, but valve buyers very often back down and select CS when the price total (and often deliverytime) comes up.

You could check both.

There is of course present the chance of galvanic corrosion CS /SS, but this should cause no great problems taking proper steps (I'm no expert on this). Very often, as example, land based treatment plants for drinking water or process plants will have SS lines but Nodular Cast Iron or steel valves.

 

[europipe]

Maybe it´s SS because it is diluted steam.
Why can´t you use ss gatevalves for it?

 

[gatossi]

europipe,
That was my first shot! to use gate valves... but I couldn't find any reference on the vendor literature (at least the one I had on hand) for 300# SS Gate Valves smaller than 1.1/2". And I need a 1" valve.

Are 1" 300# SS Gate valves readily available in the market?
I think this should have been my question in the first place! je

Regards,

Gabriel

 

[europipe]

I know Velan(Tyco) has them.

http://www.velan.com/products/catalogs/sf.htm

 

[JimCasey]

No shortage of small gate, globe, check valves here:

http://www.flowserve.com/eim/Litera...ustrySearchTerm=*&litKeywordSearchTerm=&litIs

this is the Vogt valve line on Flowserve.com. They seem to specialize in small steam valves.

If the steam is condensing, and you open the valve to drain the condensate to atmosphere, initially the condensate will cavitate, then flash, then there will be a 2-phase flow before dry steam flows thru the valve. Dry steam is the least damaging, but stainless resists flashing and 2-phase damage and is somewhat better at resisting cavitation damage.

 

[europipe]

For draining (and instr. connections)you can use the valvolets (fell in love with them).
Bellow sealed vlv's are preferrable in your service but they cost 3 times as much.
Don't you have a pipespec?

Greetings

 

[quark]

I prefer piston valves for steam applications.

 

[gatossi]

Europipe,
The pipe spec does not cover 1" gate valves, only have globe valve at 1". Therefore I have to ways of action... either to use the globe valve and do nothing else... or try to engineer the valve spec and bring the gate valve spec down to 1".

Quark,
All the CS spec use piston valves for steam applications, I should find out if our vendor has SS piston valves. Just as a matter of interest. Why do you prefer piston valves for steam?

Regards,
Gabriel

 

[quark]

The advantage with piston valves is the soft seating arrangement. After initial heating, if you maintain the bonnet bolt recommended torque, they are almost leak free for years. My experience with both steam and thermic fluids (including vaporizers) has been too good.